Pregnancy Due Date Calculator
Estimate your due date and current week of pregnancy from your last period.
The most common way to estimate a due date uses the first day of your last period as a starting point, adding 280 days (40 weeks) — the standard convention used by most pregnancy apps and many healthcare providers as a first estimate.
Why this is an estimate, not a guarantee
Naegele's rule assumes a standard 28-day cycle — actual cycle length varies between individuals, which is why an early ultrasound often provides a more precise due date. Only about 5% of babies are actually born on their exact calculated due date.
Frequently asked questions
Why did my doctor give me a different due date?
Ultrasound measurements are considered more accurate than last-period-based calculations, particularly if your cycle isn't a standard 28 days.
Is it normal to deliver before or after the due date?
Yes — full-term delivery is considered anywhere from about 37 to 42 weeks.